Does Preoperative Function Affect the Outcome Following Pyeloplasty in Poorly Functioning Kidneys among Pediatric Population?

AIM: To determine the efficacy and outcome of pyeloplasty in poorly functioning kidneys in the pediatric population and whether pyeloplasty could be offered as an upfront procedure in such patient population, instead of nephrectomy.
MATERIALS AND METHODS: A retrospective data analysis of 83 patients who underwent pyeloplasty in poorly functioning kidneys from 2010 to 2015 was performed. Success was defined based on improvement in symptoms, stable or improved function, and better drainage on post-operative Tc-99m Diethylene Triamine Pentaacetic acid scan instead of DTPA scan renography done after 3 months and yearly thereafter.
RESULTS: Eighty-three patients with a mean age of 6.8 ± 2.88 years with poor function on isotope renogram (<30%) were included in the study. Three patients were excluded in view of postoperative outflow obstruction. Out of the remaining 80 patients, 56 were male and 24 were female. They were divided into two groups based on preoperative differential renal function (DRF), Group I (n = 26) having preoperative DRF of <10% and Group II (n = 54) having preoperative DRF of 10%-30%. All patients underwent laparoscopic dismembered pyeloplasty with ureteral stenting. The mean DRF improved from 7.58 ± 2.39 to 29.71 ± 5.16 postoperatively in Group I. However, in Group II, DRF improved from 20.81 ± 5.68 to 37.25 ± 7.11 postoperatively. At a follow-up of 24 months, the overall success rate was 98%.
CONCLUSION: Pyeloplasty gives good intermediate-term results even in extremely poorly functioning kidneys and an upfront pyeloplasty instead of nephrectomy should be offered to all pediatric patients irrespective of preoperative function. Copyright:

INTRODUCTION

Ureteropelvic junction obstruction (UPJO), which is characterized by obstruction to flow of urine from renal pelvis to the ureter, is one of the common causes of hydronephrosis. The reported incidence of this disease is 1:500 live births.[1] It is the most common anatomical cause of antenatal hydronephrosis. Although it is a congenital disease, but it can largely remain asymptomatic and may present in adulthood. The indications for intervention include presence of symptoms, renal impairment, infection, development of stones, and rarely hypertension.[2] Due to long-standing obstruction, some of these hydronephrotic kidneys tend to lose their function and become poorly or non-functioning at a time. Pyeloplasty remains the gold standard procedure when intervention is warranted. However, the choice between pyeloplasty or nephrectomy in cases of poorly functioning kidneys is a matter of debate. As a general rule, the kidneys with function <10% are considered not salvageable, and hence, nephrectomy is advocated. However, contemporary studies suggest that even in the presence of poor function, pyeloplasty instead of nephrectomy should be performed.[3] The argument in favor of pyeloplasty is that in the presence of obstruction, the predictability of function of kidney is not accurate, and second, there is good probability of functional recovery after relief of obstruction in young children due to good renal reserve; hence, whatever available, the functional parenchyma should be preserved.[4] At our institute, we perform pyeloplasty in all pediatric UPJ obstruction patients irrespective of renal function. We conducted this study to present our results of pyeloplasty performed in poorly functioning kidneys among pediatric population. The aim of this study was to compare the outcome of pyeloplasty among poorly functioning kidneys by dividing them into two groups. Group I included patients having function <10%, which is generally considered as an indication for nephrectomy. Group II consisted of patients having function between 10% and 30%.

MATERIALS AND METHODS

It was a retrospectively conducted study from 2010 to 2015 and included 83 patients who underwent pyeloplasty for poorly functioning kidneys due to UPJO. UPJ obstruction was defined as hydronephrosis with no dilatation of ureter along with obstructed pattern on DTPA renogram. Inclusion criteria were patients with unilateral UPJ obstruction with differential renal function (DRF) <30%. Indications of surgery were pain, decrease in renal function, and infection. Patients with bilateral obstruction, secondary UPJ obstruction associated with vesicoureteric reflux, and those who did not have a minimum follow-up of at least 2 years were excluded from the study. After institution board approval, records of all such patients were analyzed. Parameters recorded were hemogram, serum creatinine, Society of Fetal Urology (SFU) grading of hydronephrosis, and parenchymal thickness in ultrasound of the abdomen; contrast-enhanced computed tomography of the abdomen, if available and DRF in diuretic renogram (99m Tc-DTPA renogram). “F” + 15 protocol for diuretic renogram was followed in all cases. SFU grading system was used to grade hydronephrosis. All patients underwent laparoscopic dismembered pyeloplasty with ureteral stent inserted in all cases, which were removed at 4–6 weeks. Postoperatively, ultrasound of the abdomen and diuretic renogram were done at 3 months, 12 months, and annually thereafter. We included patients who had at least 2 years of follow-up as most of the recurrences occur within the first 2 years. Three patients had postoperative outflow obstruction and hence were excluded from the study. We divided the remaining 80 patients into two groups. Group I included patients who had DRF <10% and Group II included patients who had DRF between 10% and 30%. We selected 10% as the cutoff value, as usually kidneys with <10% function are considered non-salvageable and are subjected to nephrectomy. Success was defined by improvement in symptoms, stable or improved function, and non-obstructed drainage on diuretic renogram. We did ultrasound in follow-up, but did not include it in analysis due to operator dependence and persistence of hydronephrosis even after a successful procedure.

RESULTS

The study included 83 patients with a mean age of 6.8 ± 2.88 years. Three patients were excluded in view of postoperative outflow obstruction. Out of 80 patients, 56 were male and 24 were female. Left side was involved in 45 (54.8%) cases, whereas the right side involvement was seen in 35 (45.2%) cases. Clinical presentation was pain in 12, UTI in 9, and abdominal mass in 10 cases. 39 patients had antenatally detected hydronephrosis, whereas 10 had incidentally detected hydronephrosis detected on ultrasound performed for other reasons.

We divided the study population into two groups depending on DRF. Group I (n = 26) consisted of patients who had preoperative DF of <10%, and patients with a preoperative DRF in between 10% and 30% constituted Group 2 (n = 54). In group I, 19 (73.1%) patients were male and 7 (26.9%) were female, whereas in group II, 37 (68.5%) patients were male and 17 (31.5%) were female. On ultrasonography, hydronephrosis was graded according to SFU grading. In group 1, Grade 2, 3, and 4 hydronephrosis was seen in 0, 12 (46.2%), and 14 (53.8%) patients, respectively. However, in Group II, Grade 2, 3, and 4 hydronephrosis was seen in 7 (13%), 33 (61.1%), and 14 (25.9%) patients, respectively. When both groups were compared by Fisher's exact test, there was no statistical difference between the two groups (P = 0.33).

We had followed up these patients at stratified and defined protocol and compared the improvement in symptoms and differential function at different time intervals. Three patients (including the boy with symptoms) had obstructed drainage during the initial follow-up and all these patients had DRF between 10% and 30%. The boy who had symptom of persistent and unrelenting pain with obstructed drainage underwent a redo pyeloplasty. The other two patients who had obstructed drainage initially were asymptomatic and were followed up and later showed unobstructed drainage at other times of follow-up. To avoid confusion in our analysis by false elevation of DRF, we excluded these three obstructed patients from the analysis.

The results of the follow-up schedule are depicted in Table 1. We found that there was consistent improvement in DRF as compared to the preoperative values at various defined time intervals. Friedman test was used for comparing improvement in DRF at 3 months, 12 months, and 24 months; it was found that both the groups had shown significant improvement in the DRF. We also had observed that though both the groups had shown statistically significant improvement in the DRF postoperatively, it was the Group II, which had shown more significant improvement (as P < 0.001).

Table 1

Intragroup comparison of differential renal function between different time intervals

Study group	Renogram Timing	Mean±SD (%)	Range (%)	P
Group 1 (n=26)	Preoperative	7.58±2.39	4–10	0.001*
	3 months	23. 20±13.36	14–52
	12 months	26.57±5.80	19–35
	24 months	29.71±5.16	24–36
Group II (n=54)	Preoperative	20.81±5.68	11–30	<0.001*
	3 months	29.72±9.66	13–54
	12 months	34.73±7.20	21–53
	24 months	37.25±7.11	25–54

SD: Standard deviation, *significant p < 0.05

We compared the DRF at various time intervals in between Group I and II using Mann–Whitney U test, the results of which are tabulated in Table 2. There is statistically significant difference in differential function at all-time intervals when group II was compared to Group I.

Table 2

Intergroup comparison of differential renal function between the study groups at different time intervals

Renogram timing	Study group	n	Mean±SD (%)	Range (%)	P
Preoperative	Group 1	26	7.58±2.39	4–10	<0.001*
	Group II	54	20.81±5.68	11–30
3 months	Group 1	26	23. 20±13.36	14–52	0.04*
	Group II	54	29.72±9.66	13–54
12 months	Group 1	26	26.57±5.80	19–35	0.006*
	Group II	54	34.73±7.20	21–53
24 months	Group 1	26	29.71±5.16	24–36	0.01*
	Group II	54	37.25±7.11	25–54

SD: Standard deviation, *significant p < 0.05

As there was significant improvement in DRF in both the groups at various time intervals, we did a pair-wise comparison in DRF improvement to know change in DRF with respect to time using Wilcoxon signed-rank test. The results of which are shown in Table 3, which shows that the maximum change in differential function in the very poorly functioning group was at 3 months.

Table 3

Comparison of differential renal function at various periods of time

DRF	P
	Overall	Group 1	Group II
Preoperative versus 3 months	<0.001*	0.02*	<0.001*
Preoperative versus 12 months	<0.001*	0.02*	<0.001*
Preoperative versus 24 months	<0.001*	0.02*	<0.001*
3 versus 12 months	<0.001*	0.24	<0.001*
3 versus 24 months	<0.001*	0.24	<0.001*
12 versus 24 months	<0.001*	0.04*	<0.001*

DRF: Differential renal function, *significant p < 0.05

DISCUSSION

UPJO is the leading cause of antenatal detected hydronephrosis, incidence of which is on a rise due to widespread usage of antenatal ultrasound and access to health-care facilities.[5] The obstruction to regular flow of urine from renal pelvis to ureter leads to development of myriad of symptoms ranging from being asymptomatic to pain, infections, hematuria, or abdominal lump. If left untreated, it may have detrimental effect on renal function and can lead to poorly or sometimes, non-functioning kidneys. Spontaneous recovery of renal function and anatomic dilatation in UPJ obstruction can occur. However, there should be stringent follow-up of these patients.[6] Whenever indicated, the pyeloplasty is the gold standard of procedure for correction of UPJ obstruction, the aim of procedure being alleviation of symptoms, provision of unobstructed urinary drainage, and prevention of renal functional deterioration.[7] Open pyeloplasty is preferred in infants, while laparoscopic procedure is commonly used in older children.[8]

The treatment decision in poorly functioning kidneys still remains a matter of debate with considerable controversies. In urological literature, studies advocating both pyeloplasty and nephrectomy are available. The general consensus in the past was to consider nephrectomy if the DRF is <10%.[9] However, of late, studies have come which favor pyeloplasty instead of nephrectomy.[1011] In our study, we have observed that kidneys with a preoperative DRF of <10% also fared well after pyeloplasty. All these patients had a significant improvement in DRF, as compared to preoperative values at defined follow-up intervals. The other group also showed a significant improvement with respect to time. This group had more improvement in comparison to Group 1, inferring that better the preoperative DRF, better is the postoperative improvement. Our results are in accordance with several other studies, which showed better recovery in moderately as compared to severely impaired kidneys.[12]

In our study, we found that after pyeloplasty, the poorly functioning kidneys showed the tendency toward recovery irrespective of their function in preoperative period. Age and sex also did not affect the postoperative recovery. An interesting observation was made in kidneys with preoperative DRF <10%. Patients in Group I (DRF <10%) showed majority of improvement during the first follow-up, i.e., 3 months after surgery (P = 0.02). Lone et al. also made such observation in their study.[13] When we compared the DRF after 3 months with that at 12 months and 24 months, we found that though that improvement had occurred, it was not significant (P = 0.24). In Group II (DRF 10%–30%), comparing DRF after 3 months with that at 12 months and 24 months, we found that statistically significant improvement in DRF at different intervals after 3 months (P = −0.001), meaning that this population had continuously and persistently improvement in differential renal function.

Bhat et al. in their study evaluated the histopathological changes as the predictors for outcome of pyeloplasty. They concluded that the presence of glomerulosclerosis, widened bowman capsule, interstitial fibrosis, and tubular atrophy in the specimen were poor predictors for renal recoverability.[14] To assess the recoverability of such poorly functioning hydronephrotic kidneys, some authors have advocated placement of nephrostomies followed by assessment of renal function. Gupta et al. in their study showed the mean improvement of 29.2% ± 12.6% in kidneys with DRF of <10% after placement of nephrostomies.[15] Such an observation was also made by Aziz et al. and had advocated the placement of nephrostomies to assess the recoverability of renal function before doing a nephrectomy.[16] In our study, we did not performed nephrostomies in any patient and did upfront pyeloplasty in all the patients instead. We feel that nephrostomy should be reserved to patients with presence of pyonephrosis, leading to signs of systemic toxicity and UPJ obstruction in bilateral or solitary kidney.

In our study, the DRF (% age) improved from 7.58 ± 2.39 to 29.71 ± 5.16 postoperatively in Group I. However, in Group II, DRF (% age) improved from 20.81 ± 5.68 to 37.25 ± 7.11 postoperatively. We have found a significant improvement in the DRF in poorly functioning kidneys postoperatively. We conclude that pyeloplasty has a good outcome and has high salvage and success rates. It should be offered to all the pediatric patients presenting with UPJ obstruction irrespective of function of the renal unit instead of nephrectomy. An upfront pyeloplasty is a feasible option with nephrostomy insertion to be reserved for pyonephrotic kidneys or UPJ obstruction in bilateral or solitary kidneys. Although we had defined follow-up protocol for all such patients, retrospective nature is one of the shortcomings of our study. Second, the sample size is small and is still smaller in group with DRF <10%. The result should be validated by prospective studies with larger sample size and long follow-up duration.

CONCLUSION

A pyeloplasty should be done in all cases of UPJ obstruction among the pediatric population irrespective of the preoperative function. A good overall recovery has been seen in patients with such presentation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.